Method and apparatus for image forming capable of effectively performing a charging process

Abstract

A method and an apparatus of controlling a charge voltage including the steps of applying, charging, detecting, and determining. The applying step applies an application voltage having a direct-current voltage and an alternating-current voltage superimposed onto the direct-current voltage to a charge-applying member to charge a charge carrier. The changing step charges the alternating-current voltage of the application voltage. The detecting step detects an alternating current flowing through the charge carrier when the charge-applying member applies the application voltage to the charge carrier. The determining step determines a value of the alternating-current voltage of the application voltage based on at least two alternating currents detected by the alternating-current detector.

1. An image forming apparatus, comprising:
 a charge carrier configured to carry a charge; 
 an AC voltage calculator configured to calculate a value of an alternating-current voltage of an application voltage based on first and second alternating-current voltages, first and second alternating currents, and a predefined reference alternating current capable of evenly charging a surface of the charge carrier; 
 a charging device configured to charge the surface of the charge carrier, the charging device comprising:
 a charge-applying device arranged parallel to and facing the charge carrier, 
 a power controller configured to apply to the charge carrier the application voltage including a direct-current voltage and the alternating-current voltage superimposed onto the direct-current voltage, 
 an alternating-current detector configured to detect an alternating current flowing through the charge carrier when the charge-applying device applies the application voltage to the charge carrier, and 
 a voltage value controller configured to determine the value of the alternating-current voltage of the application voltage based on at least two alternating currents detected by the alternating-current detector; and 
 
 an instructing mechanism configured to generate an instruction, wherein 
 the voltage value controller is configured to determine the alternating-current voltage value of the application voltage in accordance with the instruction generated by the instructing mechanism, 
 the at least two alternating currents include the first and second alternating currents detected when the power controller applies the first and second alternating-current voltages, respectively, of the application voltage to the charge-applying device, and 
 the first and second alternating-current voltages are different from each other and each have a value at least double a discharge-start voltage that initiates an electrical discharge from the charge-applying device to the charge carrier. 
 
   
   
     2. The image forming apparatus of  claim 1 , wherein the charge carrier is further configured to carry an electrostatic image. 
   
   
     3. The image forming apparatus of  claim 1 , further comprising:
 an environment detector arranged at a position close to the charge-applying device and configured to detect at least one of ambient temperature and humidity; and 
 a reference AC adjuster configured to change the predefined reference alternating current in accordance with a detection result detected by the environment detector. 
 
   
   
     4. The image forming apparatus of  claim 3 , wherein the voltage value controller is configured to determine the alternating-current voltage value of the application voltage upon a detection of an environmental change through the environment detector. 
   
   
     5. The image forming apparatus of  claim 1 , wherein the charging device further includes an identification memory chip configured to store the predefined reference alternating current value. 
   
   
     6. The image forming apparatus of  claim 1 , further comprising:
 an image density adjuster configured to adjust a density of an image after a determination of the alternating-current voltage value of the application voltage by the voltage value controller. 
 
   
   
     7. The image forming apparatus of  claim 1 , wherein the voltage value controller is configured to determine the alternating-current voltage value of the application voltage after a recovery from a jam of a recording sheet. 
   
   
     8. The image forming apparatus of  claim 1 , wherein the voltage value controller is configured to determine the alternating-current voltage value of the application voltage when a main power switch of the apparatus is turned on. 
   
   
     9. The image forming apparatus of  claim 1 , further comprising:
 a door arranged at a window accessible to the charging device and configured to be opened and closed when the charging device is replaced, wherein 
 the voltage value controller is configured to determine the alternating-current voltage value of the application voltage when the door is opened and closed. 
 
   
   
     10. The image forming apparatus of  claim 5 , wherein
 the charge carrier and the charging device are assembled together in a process cartridge that is exchangeable as a whole, and the identification memory chip storing the predefined reference alternating current is mounted to the process cartridge, and 
 the AC voltage calculator is configured to calculate the alternating-current voltage of the application voltage based on the predefined reference alternating current value stored in the identification memory chip. 
 
   
   
     11. An image forming apparatus, comprising:
 a charge carrier configured to carry a charge; 
 a charging device configured to charge a surface of the charge carrier, the charging device comprising:
 a charge-applying device arranged parallel to and facing the charge carrier, 
 a power controller configured to apply to the charge carrier an application voltage including a direct-current voltage and an alternating-current voltage superimposed onto the direct-current voltage, 
 an alternating-current detector configured to detect an alternating current flowing through the charge carrier when the charge-applying device applies the application voltage to the charge carrier, and 
 a voltage value controller configured to determine a value of the alternating-current voltage of the application voltage based on at least two alternating currents detected by the alternating-current detector; and 
 
 an instructing mechanism configured to generate an instruction, wherein 
 the voltage value controller is configured to determine the alternating-current voltage value of the application voltage in accordance with the instruction generated by the instructing mechanism, 
 the charge-applying device is configured to rotate with the charge carrier, 
 the image forming apparatus includes a run detector configured to detect a travel distance of a surface of the charge-applying device by a rotation thereof, and 
 the voltage value controller is configured to determine the alternating-current voltage value of the application voltage when the travel distance of the surface of the charge-applying device reaches a predetermined value. 
 
   
   
     12. A charging device, comprising:
 a charge carrier configured to carry a charge; 
 a charging device configured to charge a surface of the charge carrier, the charging device comprising:
 a charge-applying device arranged parallel to and facing the charge carrier, 
 a power controller configured to apply to the charge carrier an application voltage including a direct-current voltage and an alternating-current voltage superimposed onto the direct-current voltage, 
 an alternating-current detector configured to detect an alternating current flowing through the charge carrier when the charge-applying device applies the application voltage to the charge carrier, and 
 a voltage value controller configured to determine an alternating-current voltage value of the application voltage based on at least two alternating currents detected by the alternating-current detector, wherein 
 the at least two alternating currents include first and second alternating currents detected when the power controller applies first and second alternating-current voltages, respectively, of the application voltage to the charge-applying device; and 
 
 an AC voltage calculator configured to calculate the alternating-current voltage of the application voltage based on the first and second alternating-current voltages, the first and second alternating currents, and a predefined reference alternating current capable of evenly charging the surface of the charge carrier, wherein 
 the first and second alternating-current voltages are different from each other and each has a value at least double a discharge-start voltage that initiates an electrical discharge from the charge-applying device to the charge carrier when a direct-current voltage is singularly applied as the application voltage to the charge-applying device. 
 
   
   
     13. The charging device of  claim 12 , further comprising:
 an environment detector arranged at a position close to the charge-applying device and configured to detect at least one of ambient temperature and humidity; and 
 a reference AC adjuster configured to change the predefined reference alternating current in accordance with a detection result detected by the environment detector. 
 
   
   
     14. The charging device of  claim 13 , wherein the voltage value controller is configured to determine the alternating-current voltage value of the application voltage upon a detection of an environmental change through the environment detector. 
   
   
     15. The charging device of  claim 12 , further comprising:
 an identification memory chip configured to store the predefined reference alternating current value.